2010

• Thomas Scharrenbach, Claudia d'Amato, Nicola Fanizzi, Rolf Grütter, Bettina Waldvogel, Abraham Bernstein, Default Logics for Plausible Reasoning with Controversial Axioms, Proceedings of the 6th International Workshop on Uncertainty Reasoning for the Semantic Web (URSW-2010), November 2010, CEUR Workshop Proceedings. (inproceedings)
  
  Using a variant of Lehmann's Default Logics and Probabilistic Description Logics we recently presented a framework that invalidates those unwanted inferences that cause concept unsatisfiability without the need to remove explicitly stated axioms. The solutions of this methods were shown to outperform classical ontology repair w.r.t. the number of inferences invalidated. However, conflicts may still exist in the knowledge base and can make reasoning ambiguous. Furthermore, solutions with a minimal number of inferences invalidated do not necessarily minimize the number of conflicts. In this paper we provide an overview over finding solutions that have a minimal number of conflicts while invalidating as few inferences as possible. Specifically, we propose to evaluate solutions w.r.t. the quantity of information they convey by recurring to the notion of entropy and discuss a possible approach towards computing the entropy w.r.t. an ABox.
  
• Thomas Scharrenbach, Rolf Grütter, Bettina Waldvogel, Abraham Bernstein, Structure Preserving TBox Repair using Defaults, Proceedings of the 23rd International Workshop on Description Logics (DL 2010), May 2010, CEUR Workshop Proceedings. (inproceedings)
  
  Unsatisfiable concepts are a major cause for inconsistencies in Description Logics knowledge bases. Popular methods for repairing such concepts aim to remove or rewrite axioms to resolve the conflict by the original logics used. Under certain conditions, however, the structure and intention of the original axioms must be preserved in the knowledge base. This, in turn, requires changing the underlying logics for repair. In this paper, we show how Probabilistic Description Logics, a variant of Reiter?s default logics with Lehmann?s Lexicographical Entailment, can be used to resolve conflicts fully-automatically and receive a consistent knowledge base from which inferences can be drawn again.
  
• Thomas Scharrenbach, Claudia d'Amato, Nicola Fanizzi, Rolf Grütter, Bettina Waldvogel, Abraham Bernstein, Unsupervised Conflict-Free Ontology Evolution Without Removing Axioms, Proceedings of the 4th International Workshop on Ontology Dynamics (IWOD 2010), November 2010, CEUR Workshop Proceedings. (inproceedings)
  
  In the beginning of the Semantic Web, ontologies were usually constructed once by a single knowledge engineer and then used as a static conceptualization of some domain. Nowadays, knowledge bases are increasingly dynamically evolving and incorporate new knowledge from different heterogeneous domains -- some of which is even contributed by casual users (i.e., non-knowledge engineers) or even software agents. Given that ontologies are based on the rather strict formalism of Description Logics and their inference procedures, conflicts are likely to occur during ontology evolution. Conflicts, in turn, may cause an ontological knowledge base to become inconsistent and making reasoning impossible. Hence, every formalism for ontology evolution should provide a mechanism for resolving conflicts. In this paper we provide a general framework for conflict-free ontology evolution without changing the knowledge representation. Using a variant of Lehmann's Default Logics and Probabilistic Description Logics, we can invalidate unwanted implicit inferences without removing explicitly stated axioms. We show that this method outperforms classical ontology repair w.r.t. the amount of information lost while allowing for automatic conflict-solving when evolving ontologies.
  
• Rolf Grütter, Thomas Scharrenbach, Bettina Waldvogel, Vague Spatio-Thematic Query-Processing - A Qualitative Approach to Spatial Closeness, Transactions in GIS 14, April 2010. (article)
  
  In order to support the processing of qualitative spatial queries, spatial knowledge must be represented in a way that machines can make use of it. Ontologies typically represent thematic knowledge. Enhancing them with spatial knowledge is still a challenge. In this article, an implementation of the Region Connection Calculus (RCC) in the Web Ontology Language (OWL), augmented by DL-safe SWRL rules, is used to represent spatio-thematic knowledge. This involves partially ordered partitions, which are implemented by nominals and functional roles. Accordingly, a spatial division into administrative regions, rather than, for instance, a metric system, is used as a frame of reference for evaluating closeness. Hence, closeness is evaluated purely according to qualitative criteria. Colloquial descriptions typically involve qualitative concepts. The approach presented here is thus expected to align better with the way human beings deal with closeness than does a quantitative approach. To illustrate the approach, it is applied to the retrieval of documents from the database of the Datacenter Nature and Landscape (DNL).
  

2009

• Rolf Grütter, Thomas Scharrenbach, A Qualitative Approach to Vague Spatio-Thematic Query Processing, Proceedings of the Terra Cognita Workshop, ISWC2009, Editor(s): Dave Kolas, Nancy Wiegand, Gary Berg-Cross, October ; 2009. (inproceedings)
  
  
• Thomas Scharrenbach, Abraham Bernstein, On the Evolution of Ontologies using Probabilistic Description Logics, Proceedings of the First ESWC Workshop on Inductive Reasoning and Machine Learning on the Semantic Web, Editor(s): Claudia d'Amato, Nicola Fanizzi, Marko Grobelnik, Agnieszka Lawrynowicz, Vojtech Svátek, June ; 2009, CEUR Workshop Proceedings. (inproceedings)
  
  Exceptions play an important role in conceptualizing data, especially when new knowledge is introduced or existing knowledge changes. Furthermore, real-world data often is contradictory and uncertain. Current formalisms for conceptualizing data like Description Logics rely upon rst-order logic. As a consequence, they are poor in addressing exceptional, inconsistent and uncertain data, in particular when evolving the knowledge base over time. This paper investigates the use of Probabilistic Description Logics as a formalism for the evolution of ontologies that conceptualize real-world data. Dierent scenarios are presented for the automatic handling of inconsistencies during ontology evolution.
  
• Bettina Bauer-Messmer, Lukas Wotruba, Kalin Müller, Sandro Bischof, Rolf Grütter, Thomas Scharrenbach, Rolf Meile, Martin Hägeli, Jürg Schenker, The Data Centre Nature and Landscape (DNL): Service Oriented Architecture, Metadata Standards and Semantic Technologies in an Environmental Information System, EnviroInfo 2009: Environmental Informatics and Industrial Environmental Protection: Concepts, Methods and Tools, Editor(s): Volker Wohlgemuth, Bernd Page, Kristina Voigt, September ; 2009, Shaker Verlag, Aachen. (inproceedings)
  
  

2008

• Thomas Scharrenbach, End-User Assisted Ontology Evolution in Uncertain Domains, The Semantic Web - ISWC 2008, 7th International Semantic Web Conference 2008, Springer. (inproceedings)
  
  
• Bettina Bauer-Messmer, Thomas Scharrenbach, Rolf Grütter, Improving an Environmental Ontology by Incorporating User-Input, Environmental Informatics and Industrial Ecology. Proceedings of the 22nd International Conference on Informatics for Environmental Protection, September 2008. (inproceedings)
  
  
• Rolf Grütter, Thomas Scharrenbach, Bettina Bauer-Messmer, Improving an RCC-Derived Geospatial Approximation by OWL Axioms, The Semantic Web - ISWC 2008, 7th International Semantic Web Conference, October 2008, Springer. (inproceedings)
  
  

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